1. Field of the Invention
The present invention relates to a mechanical time piece having a balance rotational angle control mechanism constituted to exert a force for restraining rotation of a balance with hairspring.
Particularly, the invention relates to a mechanical time piece having a balance rotational angle control mechanism including a balance magnet provided to a balance with hairspring and a coil arranged to be related to the balance magnet.
2. Background Information
According to a conventional mechanical time piece, as shown in FIG. 13 and FIG. 14, a movement (machine body) 1100 of a mechanical time piece is provided with a main plate 1102 constituting a base plate of the movement. A winding stem 1110 is rotatably integrated to a winding stem guide hole 1102a of the main plate 1102. A dial 1104 (shown in FIG. 14 by an imaginary line) is attached to the movement 1100.
Generally, in both sides of the main plate, a side thereof having the dial is referred to as xe2x80x9cback sidexe2x80x9d of the movement and a side thereof opposed to the side having the dial is referred to as xe2x80x9cfront sidexe2x80x9d of the movement. A train wheel integrated to the xe2x80x9cfront sidexe2x80x9d of the movement is referred to as xe2x80x9cfront train wheelxe2x80x9d and a train wheel integrated to the xe2x80x9cback sidexe2x80x9d of the movement is referred to as xe2x80x9cback train wheelxe2x80x9d.
A position in the axis line direction of the winding stem 1110 is determined by a switch apparatus including a setting lever 1190, a yoke 1192, a yoke spring 1194 and a setting lever jumper 1196. A winding pinion 1112 is provided rotatably at a guide shaft portion of the winding stem 1110. When the winding stem 1110 is rotated in the state in which the winding stem 1110 is disposed at a first winding stem position (0-stage) on a side most proximate to the inner side of the movement along the rotational axis line, the winding pinion 1112 is rotated via rotation of a clutch wheel. A crown wheel 1114 is rotated by rotation of the winding pinion 1112. A ratchet wheel 1116 is rotated by rotation of the crown wheel 1114. By rotating the ratchet wheel 1116, a mainspring 1122 contained in a barrel complete 1120 is wound up. A center wheel and pinion 1124 is rotated by rotation of the barrel complete 1120. An escape wheel and pinion 1130 is rotated via rotation of a fourth wheel and pinion 1128, a third wheel and pinion 1126 and the center wheel and pinion 1124. The barrel complete 1120, the center wheel and pinion 1124, the third wheel and pinion 1126 and the fourth wheel and pinion 1128 constitute a front train wheel.
An escapement and speed control apparatus for controlling rotation of the front train wheel includes a balance with hairspring 1140, the escape wheel and pinion 1130 and a pallet fork 1142. The balance with hairspring 1140 includes a balance stem 1140a, a balance wheel 1140b and a hairspring 1140c. Based on rotation of the center wheel and pinion 1124, a cannon pinion 1150 is simultaneously rotated. A minute hand 1152 attached to the cannon pinion 1150 displays xe2x80x9cminutexe2x80x9d. The cannon pinion 1150 is provided with a slip mechanism relative to the center pinion and wheel 1124. Based on rotation of the cannon pinion 1150, via rotation of a minute wheel, an hour wheel 1154 is rotated. An hour hand 1156 attached to the hour wheel 1154 displays xe2x80x9chourxe2x80x9d.
The barrel complete 1120 is supported rotatably by the main plate 1102 and a barrel bridge 1160. The center wheel and pinion 1124, the third wheel and pinion 1126, the fourth wheel and pinion 1128 and the escape wheel and pinion 1130 are supported rotatably by the main plate 1102 and a train wheel bridge 1162. The pallet fork 1142 is supported rotatably by the main plate 1102 and a pallet bridge 1164. The balance with hairspring 1140 is supported rotatably by the main plate 1102 and a balance bridge 1166.
The hairspring 1140c is a leaf spring in a helical (spiral) shape having a plural turn number. An inner end portion of the hairspring 1140c is fixed to a hairspring holder 1140d fixed to the balance stem 1140a and an outer end portion of the hairspring 1140c is fixed via a hairspring stud 1170a attached to a stud support 1170 fixed to the balance bridge 1166 by fastening screws.
A regulator 1168 is attached rotatably to the balance bridge 1166. A hairspring bridge 1168a and a hairspring rod 1168b are attached to the regulator 1168. A portion of the hairspring 1140c proximate to the outer end portion is disposed between the hairspring bridge 1168a and the hairspring rod 1168b. 
Generally, according to a conventional representative mechanical timepiece, as shown by FIG. 8, with elapse of a duration time period of rewinding the mainspring from a state in which the mainspring has completely been wound up (fully wound state), mainspring torque is reduced. For example, in the case of FIG. 8, the mainspring torque is about 27 g.cm in the fully wound state, becomes about 23 g.cm after elapse of 20 hours from the fully wound state and becomes about 18 g.cm after elapse of 40 hours from the fully wound state.
Generally, according to a conventional representative mechanical time piece, as shown by FIG. 9, when the mainspring torque is reduced, the swing angle of the balance with hairspring is also reduced. For example, in the case of FIG. 9, when the mainspring torque is 25-28 g.cm, the swing angle of the balance with hairspring is about 240-270 degree and when the mainspring torque is 20-25 g.cm, the swing angle of the balance with hairspring is about 180-240 degree.
In reference to FIG. 10, there is shown a transitional change of instantaneous rate with regard to swing angle of a balance with hairspring according to a conventional representative mechanical time piece (numerical value indicating accuracy of time piece). In this case, the xe2x80x9cinstantaneous ratexe2x80x9d is defined as xe2x80x9ca value indicating gain or loss of a mechanical time piece after elapse of one day after the mechanical time piece is assumed to be left for one day while maintaining state or environment of swing angle of a balance with hairspring or the like when the rate is measuredxe2x80x9d. In the case of FIG. 10, when a swing angle of a balance with hairspring is equal to or larger than 240 degree or is equal to or smaller than 200 degree, the instantaneous rate is retarded.
For example, according to a conventional representative time piece, as shown by FIG. 10, when the swing angle of the balance with hairspring falls in a range of about 200 through 240 degree, the instantaneous rate is about 0 through 5 seconds/day (gain of 0 through 5 seconds per day), however, when the swing angle of the balance with hairspring is about 170 degree, the instantaneous rate becomes about xe2x88x9220 seconds/day (loss of about 20 seconds per day).
In reference to FIG. 12, there is shown a transitional change of elapse time and instantaneous rate when a mainspring is rewound from a fully wound state in a conventional representative mechanical time piece. In this case, in the conventional mechanical time piece, xe2x80x9cratexe2x80x9d indicating gain of the timepiece or loss of the time piece per day, is provided by integrating instantaneous rate with regard to elapse time of rewinding the balance with hairspring from a fully wound state, which is indicated in FIG. 12 by an extremely slender line, over 24 hours.
Generally, according to the conventional mechanical timepiece, with elapse of duration time period of rewinding the mainspring from the fully wound state, the mainspring torque is reduced, the swing angle of the balance with hairspring is also reduced and accordingly, the instantaneous rate is retarded. Therefore, according to the conventional mechanical timepiece, by estimating loss of the time piece after elapse of the duration time period of 24 hours, instantaneous rate when the mainspring is brought into the fully wound state, is previously gained and previously adjusted such that the xe2x80x9cratexe2x80x9d indicating gain of the time piece or loss of the time piece per day becomes positive.
For example, according to the conventional representative time piece, as shown by the extremely slender line in FIG. 12, although in the fully wound state, the instantaneous rate is about 3 seconds/day (gain of about 3 seconds per day), after elapse of 20 hours from the fully wound state, the instantaneous rate becomes about xe2x88x923 seconds/day (loss of about 3 seconds per day), after elapse of 24 hours from the fully wound state, the instantaneous rate becomes about xe2x88x928 seconds per day (loss of about 8 seconds per day) and after elapse of 30 hours from the fully wound state, the instantaneous rate becomes about xe2x88x9216 seconds/day (loss of about 16 seconds per day).
Further, as a conventional apparatus of adjusting a swing angle of a balance with hairspring, there is disclosed in Japanese Utility Model Laid-Open No. 41675/1979, a constitution having a swing angle adjusting plate exerting braking force to a balance with hairspring by generating eddy current at each time of pivotal approach of a magnet of the balance with hairspring.
Further, as shown by FIG. 36, a conventional coreless motor 2100 is provided with a shaft 2102, a magnet yoke 2104 fixed to the shaft 2102 and a drive magnet 2106 fixed to the magnet yoke 2104. A stator yoke 2110 is provided rotatably to the shaft 2102 via a bearing 2112. A printed circuit board 2114 is fixed to the stator yoke 2110. A drive coil 2116 is fixed to the printed circuit board 2114 to be opposed to the drive magnet 2106 and spaced apart therefrom. By applying current to the drive coil 2116, the drive magnet 2106, the magnet yoke 2104 and the shaft 2102 are constituted to rotate.
It is an object of the invention to provide a mechanical time piece having a balance rotational angle control mechanism capable of controlling a swing angle of a balance with hairspring to fall in a constant range.
Further, it is an object of the invention to provide a mechanical time piece having excellent accuracy in which a change in a rate is in considerable even after elapse of an elapse time period from a fully wound state of a mainspring by providing a novel balance rotational angle control mechanism.
Further, it is an object of the invention to provide a mechanical time piece constituted such that a balance rotational angle control mechanism includes a balance magnet provided at a balance with hairspring and a coil unit arranged to relate to the balance magnet and constituted such that fabrication and assembly of parts are facilitated.
According to an aspect of the invention, there is provided a mechanical time piece characterized in that in a mechanical time piece having a main plate constituting a base plate of the mechanical time piece, a mainspring constituting a power source of the mechanical time piece, a front train wheel rotated by a rotational force when the mainspring is rewound and an escapement and speed control apparatus for controlling rotation of the front train wheel in which the escapement and speed control apparatus includes a balance with hairspring alternately repeating right rotation and left rotation, an escape wheel and pinion rotated based on the rotation of the front train wheel and a pallet fork for controlling rotation of the escape wheel and pinion based on operation of the balance with hairspring, the mechanical time piece comprising a switch mechanism constituted to output a signal of ON when a rotational angle of the balance with hairspring becomes equal to or larger than a predetermined threshold and output a signal of OFF when the rotational angle of the balance with hairspring does not exceed the threshold, and a balance rotational angle control mechanism constituted to exert a force for restraining rotation of the balance with hairspring to the balance with hairspring when the switch mechanism outputs the signal of ON.
According to the mechanical time piece of the aspect of the invention, the switch mechanism is constituted to output the signal of ON when a hairspring provided at the balance with hairspring is brought into contact with terminal members constituting a switch lever.
Further, according to the mechanical time piece of the aspect of the invention, the balance rotational angle control mechanism includes a balance magnet provided to the balance with hairspring and a plurality of coils arranged to be capable of exerting a magnetic force to the balance magnet and the coils are constituted to exert the magnetic force to the balance magnet to thereby restrain the rotation of the balance with hairspring when the switch mechanism outputs the signal of ON and not to exert the magnetic force to the balance magnet when the switch mechanism outputs the signal of OFF.
Further, the mechanical time piece of the invention is provided with a circuit board having patterns for conducting the plurality of coils.
By using the balance rotational angle control mechanism constituted in this way, the rotational angle of the balance with hairspring of the mechanical time piece can effectively be controlled, thereby, accuracy of the mechanical time piece can be promoted.
Further, according to the mechanical time piece of the invention, it is preferable that wiring portions of the plurality of coils are arranged on a side of a main plate of the circuit board.
Further, according to the mechanical time piece of the invention, it is preferable that the plurality of coils are attached to a coil bridge and the circuit board is attached to the coil bridge and the coil bridge is guided by a bearing member provided at the main plate.
Further, according to the mechanical time piece of the invention, it is preferable that the plurality of coils are attached to coil bridges provided respectively separately, the coil bridges are respectively attached to the circuit board and the coil bridges are guided by the guide holes respectively provided at the main plate.
Further, according to the mechanical time piece of the invention, it is preferable that the circuit board is provided with patterns for conducting the plurality of coils on one side thereof and is provided with patterns for connecting lead wires for conducting the switch mechanism on other side thereof.
Further, according to the mechanical time piece of the invention, it is preferable that the plurality of coils are connected in series by the patterns provided to the circuit board.
By constituting in this way, the plurality of coils can be arranged efficiently in a small space and the plurality of coils can firmly be conducted.
Further, according to the mechanical time piece of the invention, it is preferable that the switch mechanism includes a first terminal member and a second terminal member and is further provided with an adjusting apparatus for changing an interval between the first terminal member and the second terminal member.
Further, according to the mechanical time piece of the invention, it is preferable that the switch mechanism includes a first terminal member and a second terminal member and is further provided with an adjusting apparatus for simultaneously moving the first terminal member and the second terminal member relative to a rotational center of the balance with hairspring.
By constituting in this way, the positions of the first terminal member and the second terminal member relative to the portion proximate to the outer end portion of the hairspring and the interval between the first terminal member and the second terminal member can effectively be adjusted.